1. Field of the Invention
The present invention relates to a touch panel, and more particularly, to a touch panel capable of detecting a position at high accuracy while reducing noise.
2. Description of the Related Art
Mutual capacitive touch panels, which detect a capacitance near an intersection between an array of a plurality of detecting electrodes and a plurality of scanning electrodes arranged in a direction crossing the detecting electrodes by the detecting electrodes and the scanning electrodes, are widespread as touch panels capable of multipoint detection (see Japanese Patent Application Laid-open No. 2005-140612 below).
In recent years, equipment including a touch panel has been reduced in thickness in order to improve a design property, and hence has a reduced distance between the detecting electrodes and a display, which is a noise source, of the touch panel, which makes the touch panel more susceptible to noise.
In recent years, in order to realize further reduction in thickness, an on-cell touch panel, in which electrodes of the touch panel are formed on a color filter substrate of a liquid crystal display, has been under development. In this case, the distance between the detecting electrodes and the display is reduced, and it is impossible to provide a shield electrode (placed between the detecting electrodes and the display) for suppressing noise from the display, to thereby increase noise.
As in the mutual system, there have been proposed many methods for removing the noise in the capacitance detection for detecting a capacitance near the intersection between the scanning electrodes and the detecting electrodes. For example, a method involves providing a reference electrode at a place which is near the detecting electrodes and is affected to the same level from the noise source, and removing noise from results detected by the detecting electrodes based on noise detected by the reference electrode. Alternatively, in a case where the reference electrode is not provided, there has been proposed a method involving calculating a common noise amount from a plurality of electrodes detected at the same time, and removing noise from results detected by the detecting electrodes based on the common noise amount.